In post-primary oil recovery operations, recovery of oil is maximized if the driven fluid is permitted to build up in a wide bank in front of the driving fluid which moves uniformly toward a producing well. To keep this bank of oil intact while moving toward a producing well, a substantially uniform permeability must exist throughout the strata. If this uniform permeability does not exist, and it generally does not, the flooding fluids will seek the areas of high permeability and channeling occurs with the appearance of excess driving fluid at the producing well. Moreover, as the more permeable strata are depleted of oils, the driving fluid has a tendency to follow these channels and further increase water production as reflected in an increased water-to-oil ratio at producing wells to the point that the process becomes economically undesirable.
It is known in the art that more uniform flood fronts can be obtained in formations of non-uniform permeability by mobility control or permeability contrast correction of the more permeable strata in the formation. A number of methods for reducing the permeability of these permeable strata have been proposed, including the injection of plugging materials into the strata which at least partially plug the permeable zones so as to achieve more uniform permeability. Some of these methods of permeability contrast correction accomplish the plugging step by the in situ formation of plugging material in the formation by the injection of one or more reaction substances which chemically react to form a solid residue. The present invention is directed to the in situ formation of water-insoluble polymers from water-soluble monomers in a manner such that selective plugging of the formation is achieved.
Accordingly, an object of this invention is to provide an improved process for the recovery of oil from subterranean oil-bearing formations.
Another object of this invention is to selectively plug high permeability zones in subterranean formations.
Another object of this invention is to increase sweep efficiency of post-primary or enhanced oil recovery operations.
Other aspects, objects and the several advantages of this invention will become readily apparent to those skilled in the art from a reading of the following detailed description of the invention and the appended claims.